wireproto: add getbundle() function getbundle(common, heads) -> bundle Returns the changegroup for all ancestors of heads which are not ancestors of common. For both sets, the heads are included in the set. Intended to eventually supercede changegroupsubset and changegroup. Uses heads of common region to exclude unwanted changesets instead of bases of desired region, which is more useful and easier to implement. Designed to be extensible with new optional arguments (which will have to be guarded by corresponding capabilities).